Conventionally, an art of a workpiece detection mechanism detecting a workpiece conveyed by a workpiece transfer mechanism in a vacuum chamber is well known. Examples thereof are described in the Patent Literatures 1 and 2.
In the art described in the Patent Literature 1, a workpiece detection mechanism (sensor or the like) detecting a workpiece is arranged outside a vacuum room (vacuum chamber), and the workpiece detection mechanism detects the workpiece (a silicon wafer, a glass substrate for a solar cell or the like) conveyed by a workpiece transfer mechanism in the vacuum room is detected. Accordingly, whether the workpiece is conveyed certainly or not can be confirmed.
However, in the art described in the Patent Literature 1, the workpiece detection mechanism (sensor or the like) is fixed to a position determined previously and can detect only that the workpiece reaches a predetermined position in a conveyance process. Accordingly, when the workpiece drops out at another position in the conveyance process, it is disadvantageous that the dropping out cannot be detected immediately.
In the art described in the Patent Literature 2, a workpiece detection mechanism is arranged in a workpiece transfer mechanism. In more detail, a sensor is arranged in an end effector (a part which moves while mounting a workpiece thereon so as to convey the workpiece) of the workpiece transfer mechanism, and a communication unit transmitting detection results of the sensor with the outside and a charging unit storing electric power to be supplied to the communication unit are arranged in a base part (a part not movable and in which the end effector is supported movably via an arm) of the workpiece transfer mechanism. Accordingly, by arranging the sensor in the end effector, the workpiece can be detected at any position in the conveyance process, and when the workpiece drops out, the dropping out can be detected immediately.
However, in the art described in the Patent Literature 2, wires connecting the sensor arranged in the end effector to the communication unit and the like arranged in the base part are arranged over the arm and the end effector. Accordingly, when the end effector moves, it is disadvantageous that the wires may be damaged in the connection part between the base part and the arm or the connection part between the arm and the end effector. Furthermore, it is disadvantageous that the action of the end effector must be restricted (for example, the range of action of each connection part is restricted) for preventing the damage of the wires.